1. Field of the Invention
The present invention relates to an air-source heat pump air conditioner.
2. Description of the Related Art
In a case where the gross floor area of a building is a predetermined area or more, each room of the building is required to take in outside air, such that the carbon dioxide concentration in the room is reduced to a reference value or lower. For example, Japanese Laid-Open Patent Application Publication No. 2004-340529 proposes an energy-saving air conditioning system that makes it possible to meet such requirement.
The energy-saving air conditioning system disclosed in Japanese Laid-Open Patent Application Publication No. 2004-340529 is configured to: cause outside air and return air, both of which serve as air-conditioning air, to undergo heat exchange in two respective heat exchangers separately, such that each of the outside air and the return air exchanges heat with a circulating refrigerant; then mix the outside air and the return air together; and supply the mixed air to a space to be air conditioned, thereby cooling or heating the space. In the case of performing cooling by the energy-saving air conditioning system, low-temperature outside air that has been cooled and dehumidified is mixed with return air that has been subjected to sensible heat cooling, and thereby a temperature and humidity controlling effect is obtained, which is the same effect as that obtained in reheat control using cold water and hot water. Thus, there are advantages in terms of energy saving and cost saving.
However, the above energy-saving air conditioning system disclosed in Japanese Laid-Open Patent Application Publication No. 2004-340529 has the following technical problems. In a case where two air-conditioning outdoor units are connected to the two respective heat exchangers and thereby two refrigeration cycles are formed, the operating time of one outdoor unit and the operating time of the other outdoor unit are not equal to each other, which results in high life-cycle cost.